"AddrPort.Port",
		"AddrPort.IsValid",
		"Prefix.IsSingleIP",
		"Prefix.Masked",
		"Prefix.IsValid",
		"PrefixFrom",
		"Prefix.Addr",
		"Prefix.Bits",
		"AddrFrom4",
		"IPv6LinkLocalAllNodes",
		"IPv6Unspecified",
		"MustParseAddr",
		"MustParseAddrPort",
		"MustParsePrefix",
		"appendDecimal",
		"appendHex",
		"uint128.addOne",
		"uint128.and",
		"uint128.bitsClearedFrom",
		"uint128.bitsSetFrom",

		resolveTCPAddrTests = append(resolveTCPAddrTests, resolveTCPAddrTest{"tcp", "[::]:4", &TCPAddr{IP: IPv6unspecified, Port: 4}, nil})
		resolveUDPAddrTests = append(resolveUDPAddrTests, resolveUDPAddrTest{"udp", "[::]:4", &UDPAddr{IP: IPv6unspecified, Port: 4}, nil})
		resolveIPAddrTests = append(resolveIPAddrTests, resolveIPAddrTest{"ip", "::", &IPAddr{IP: IPv6unspecified}, nil})
	}

	ifi := loopbackInterface()
	if ifi != nil {

	// Output:
	// true
	// false
	// true
	// false
}

func ExampleIP_IsUnspecified() {
	ipv6Unspecified := net.ParseIP("::")
	ipv6Specified := net.ParseIP("fe00::")
	ipv4Unspecified := net.ParseIP("0.0.0.0")
	ipv4Specified := net.ParseIP("8.8.8.8")

	fmt.Println(ipv6Unspecified.IsUnspecified())
	fmt.Println(ipv6Specified.IsUnspecified())
	fmt.Println(ipv4Unspecified.IsUnspecified())

	if err != nil {
		return nil, err
	}
	// Issue 18806: if the machine has halfway configured
	// IPv6 such that it can bind on "::" (IPv6unspecified)
	// but not connect back to that same address, fall
	// back to dialing 0.0.0.0.
	if len(ips) == 1 && ips[0].IP.Equal(IPv6unspecified) {
		ips = append(ips, IPAddr{IP: IPv4zero})
	}

	var filter func(IPAddr) bool
	if net != "" && net[len(net)-1] == '4' {

		[]byte("2001:db8::1:0:0:1"),
		nil,
	},
	{
		IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0xa, 0, 0xb, 0, 0xc, 0, 0xd},
		"2001:db8::a:b:c:d",
		[]byte("2001:db8::a:b:c:d"),
		nil,
	},
	{
		IPv6unspecified,
		"::",
		[]byte("::"),
		nil,
	},

	// IP wildcard equivalent address in Dial/Listen API
	{
		nil,
		"<nil>",
		nil,
		nil,
	},

	// Opaque byte sequence
	{

				return err
			}
			addr := *addr
			switch fd.family {
			case syscall.AF_INET:
				addr.IP = IPv4zero
			case syscall.AF_INET6:
				addr.IP = IPv6unspecified
			}
			laddr = &addr
		}
	}
	var err error
	var lsa syscall.Sockaddr
	if lsa, err = laddr.sockaddr(fd.family); err != nil {
		return err
	}

	if ctrlCtxFn != nil {

			std:  net.IPv6linklocalallrouters,
		},
		{
			name: "IPv6 loopback",
			ip:   IPv6Loopback(),
			std:  net.IPv6loopback,
		},
		{
			name: "IPv6 unspecified",
			ip:   IPv6Unspecified(),
			std:  net.IPv6unspecified,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			want := tt.std.String()
			got := tt.ip.String()

			if got != want {

	IPv4zero      = IPv4(0, 0, 0, 0)         // all zeros
)

// Well-known IPv6 addresses
var (
	IPv6zero                   = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	IPv6unspecified            = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	IPv6loopback               = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}

// IPv6Loopback returns the IPv6 loopback address ::1.
func IPv6Loopback() Addr { return AddrFrom16([16]byte{15: 0x01}) }

// IPv6Unspecified returns the IPv6 unspecified address "::".
func IPv6Unspecified() Addr { return Addr{z: z6noz} }

// IPv4Unspecified returns the IPv4 unspecified address "0.0.0.0".
func IPv4Unspecified() Addr { return AddrFrom4([4]byte{}) }

pkg net/netip, func AddrFromSlice([]uint8) (Addr, bool)
pkg net/netip, func AddrPortFrom(Addr, uint16) AddrPort
pkg net/netip, func IPv4Unspecified() Addr
pkg net/netip, func IPv6LinkLocalAllNodes() Addr
pkg net/netip, func IPv6Unspecified() Addr
pkg net/netip, func MustParseAddr(string) Addr
pkg net/netip, func MustParseAddrPort(string) AddrPort
pkg net/netip, func MustParsePrefix(string) Prefix
pkg net/netip, func ParseAddr(string) (Addr, error)